1. Field of the Invention
The present invention relates to an apparatus for detecting the feeding of paper in which holes, which are provided along longitudinal margins at both sides of the paper, are optically detected in order to monitor how the paper is fed.
2. Description of the Prior Art
Referring to FIG. 1, in accordance with a conventional apparatus for detecting paper feeding, light from a light emitting element 3, such as a light emitting diode, collides against a paper 1 when the paper 1 is located above the light emitting element 3 so that a strong reflected light arrives at a light receiving element 4, such as a photo-transistor or the like. When a hole 2 in the paper is brought into alignment with the light emitting element 3 as shown in FIG. 2, the light from the light emitting element 3 passes through the hole 2 and collides against a non-reflecting, black paper retainer plate 5 which is rotatably mounted on a support of a paper feeding tractor (not shown). Accordingly, a weak, irregular reflected light arrives at the light receiving element 4.
In FIGS. 1 and 2, the solid arrow line denotes a strong light, while the chained arrow line denotes a weak light. The light receiving element 4 determines whether the reflected light is strong or weak in order to monitor how the paper is being fed. However, if a colored paper 8 which does not have a large reflection factor is being fed, the light reflected from the colored paper 8 is weak and has an intensity which is almost the same as the irregular light reflected from the paper retainer plate 5. Accordingly, it is difficult and sometimes impossible for the light receiving element 4 to sense whether the light has been reflected from the paper 8 or from the paper retainer plate 5. In other words, it thus becomes impossible to detect the holes 2, and the feeding of the paper is sometimes erroneously detected as being abnormal, in spite of the fact that the paper is being fed normally.